Highly linear lithium niobate Michelson interferometer modulators assisted by spiral Bragg grating reflectors.

Highly linear electro-optic modulators are key components in analog microwave photonic links, offering on-chip direct mixing of optical and RF fields. In this work, we demonstrate a monolithic integrated Michelson interferometer modulator on thin-film lithium niobate (LN), that achieves linearized performance by modulating Bragg grating reflectors placed at the end of Michelson arms. The modulator utilizes spiral-shaped waveguide Bragg gratings on Z-cut LN with top and bottom electrodes to realize extensive reflectors, essential for linearized performance, in a highly integrated form.

Investigating Substrate Loss in MEMS Acoustic Resonators and On-Chip Inductors.

This work studies the influence of substrate loss on the performance of acoustic resonators and on-chip inductors and investigates the effective substrate resistivity of seven commonly used substrates in silicon-based devices. The substrates include X-cut lithium niobate (LiNbO) film with two different thicknesses (400 nm and 1.6 [Formula: see text]) on high-resistivity Si (HR-Si) and amorphous Si wafers, SiO film with two different thicknesses on HR-Si, and bare HR-Si.

Compact MZI modulators on thin film Z-cut lithium niobate.

In this paper, we designed, implemented, and characterized compact Mach-Zehnder interferometer-based electro-optic modulators. The modulator utilizes spiral-shaped optical waveguides on Z-cut lithium niobate and the preeminent electro-optic effect which is applied using top and bottom electrodes. Optical waveguides are made of rib etched lithium niobate waveguides with bottom silicon oxide cladding, while SU8 polymer covers the top and sides of the rib waveguides.

Lateral Spurious Mode Suppression in Lithium Niobate A1 Resonators.

This work presents an improved design that exploits dispersion matching to suppress the spurious modes in the lithium niobate first-order antisymmetric (A1) Lamb wave mode resonators. The dispersion matching in this work is achieved by micro-machining the lithium niobate thin film to balance the electrical and mechanical loadings of electrodes. In this article, the dispersion matchings of the A1 mode in lithium niobate based on different metals are analytically modeled and validated with finite-element analysis.

L- and X-Band Dual-Frequency Synthesizer Utilizing Lithium Niobate RF-MEMS and Open-Loop Frequency Dividers.

This article presents an 8.6-GHz oscillator utilizing the third-order antisymmetric overtone ( A ) in a lithium niobate (LiNbO) radio frequency microelectromechanical systems (RF-MEMS) resonator. The oscillator consists of an acoustic resonator in a closed loop with cascaded RF tuned amplifiers (TAs) built on Taiwan Semiconductor Manufacturing Company (TSMC) RF general purpose (GP) 65-nm complementary metal-oxide semiconductor (CMOS).

A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air.

This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO; LN) MEMS resonator array up to 500 °C in air. After a high-temperature burn-in treatment, device quality factor () was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500 °C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.

Wideband Hybrid Monolithic Lithium Niobate Acoustic Filter in the K-Band.

This article presents the design approach and the first demonstration of a wideband hybrid monolithic acoustic filter in the K -band, which exceeds the limitation of electromechanical coupling on the fractional bandwidth (FBW) of acoustic filters. The hybrid filter utilizes the codesign of electromagnetic (EM) and acoustic to attain wide bandwidth while keeping the advantages of small sizes and high Q in the acoustic domain. The performance trade space and design flow of the hybrid filter are also presented in this article, which allows this technology to be applied for filters with different center frequencies and FBWs.

Ultra-efficient and fully isotropic monolithic microring modulators in a thin-film lithium niobate photonics platform.

The large electro-optic coefficient, r, of thin-film lithium niobate (LN) on insulator makes it an excellent material platform for high-efficiency optical modulators. Using the fundamental transverse magnetic optical mode in Z-cut LN enables isotropic in-plane devices; however, realizing a strong vertical electric field to capitalize on r has been challenging. Here we present a symmetric electrode configuration to boost the vertical field strength inside a fully-etched single-mode LN waveguide.

Acoustically driven electromagnetic radiating elements.

The low propagation loss of electromagnetic radiation below 1 MHz offers significant opportunities for low power, long range communication systems to meet growing demand for Internet of Things applications. However, the fundamental reduction in efficiency as antenna size decreases below a wavelength (30 m at 1 MHz) has made portable communication systems in the very low frequency (VLF: 3-30 kHz) and low frequency (30-300 kHz) ranges impractical for decades. A paradigm shift to piezoelectric antennas utilizing strain-driven currents at resonant wavelengths up to five orders of magnitude smaller than electrical antennas offers the promise for orders of magnitude efficiency improvement over the electrical state-of-the-art.

Low-Loss Unidirectional Acoustic Focusing Transducer in Thin-Film Lithium Niobate.

In this work, we present gigahertz low-loss unidirectional acoustic focusing transducers in thin-film lithium niobate. The design follows the anisotropy of fundamental symmetric (S0) waves in X-cut lithium niobate. The implemented acoustic delay line testbed consisting of a pair of the proposed transducers shows a low insertion loss of 4.

Fundamental electro-optic limitations of thin-film lithium niobate microring modulators.

We investigate the impact of waveguide curvature on the electro-optic efficiency of microring resonators in thin-film X-cut or Y-cut lithium niobate (in-plane extraordinary axis) and derive explicit relations on the response. It is shown that such microring modulators have a fundamental upper bound on their electro-optic performance (∼50% filling factor) which corresponds to a specific arrangement of metal electrodes surrounding the microring and yields nearly identical results for X-cut and Y-cut designs. We further show that this limitation does not exist (i.

A Wideband Oscillator Exploiting Multiple Resonances in Lithium Niobate MEMS Resonator.

This article presents a comprehensive guide to codesign lithium niobate (LiNbO) lateral overtone bulk acoustic resonators (LOBARs) and voltage-controlled oscillators (VCOs) using discrete components on a printed circuit board (PCB). The analysis focuses on understanding the oscillator-level tradeoffs between the number of locked tones, frequency stability, tuning range, power consumption, and phase noise. Moreover, this article focuses on understanding the relationship between the abovementioned specifications and the different LOBAR parameters, such as electromechanical coupling ( k ), quality factor ( Q ), transducer design, and the resonator size.

GHz Low-Loss Acoustic RF Couplers in Lithium Niobate Thin Film.

We present the first group of GHz low-loss acoustic radio frequency (RF) couplers using the fundamental symmetric (S0) mode in X-cut lithium niobate thin films. The demonstrated multistrip couplers (MSCs) significantly surpass the insertion loss (IL) and the operating frequency of the previous works in more compact structures, thanks to the large electromechanical coupling and low loss of S0 in lithium niobate. The design space of S0 MSCs is first explored.

Monolithic mtesla-level magnetic induction by self-rolled-up membrane technology.

Monolithic strong magnetic induction at the mtesla to tesla level provides essential functionalities to physical, chemical, and medical systems. Current design options are constrained by existing capabilities in three-dimensional (3D) structure construction, current handling, and magnetic material integration. We report here geometric transformation of large-area and relatively thick (~100 to 250 nm) 2D nanomembranes into multiturn 3D air-core microtubes by a vapor-phase self-rolled-up membrane (S-RuM) nanotechnology, combined with postrolling integration of ferrofluid magnetic materials by capillary force.

A Unidirectional Transducer Design for Scaling GHz AlN-Based RF Microsystems.

In this work, we present a novel unidirectional transducer design for frequency scaling aluminum nitride (AlN)-based radio frequency (RF) microsystems. The proposed thickness-field-excited single-phase unidirectional transducers (TFE-SPUDT) adopt 5/16 wavelength electrodes and, thus, enable efficient piezoelectric transduction with better frequency scalability. The design space of the TFE-SPUDT is theoretically explored and validated using the acoustic delay line (ADL) testbeds.

Characterization of an Electronic Corneal Prosthesis System.

Purpose: Corneal opacity is a leading cause of reversible blindness worldwide. An electronic corneal prosthesis, or intraocular projector, could potentially restore high-quality vision without need for corneal clarity.

Materials And Methods: Four intraocular projection systems were constructed from commercially available electronic components and encased in biocompatible plastic housing.

GHz Broadband SH0 Mode Lithium Niobate Acoustic Delay Lines.

We present the first group of GHz broadband SH0 mode acoustic delay lines (ADLs). The implemented ADLs adopt unidirectional transducer designs in a suspended X-cut lithium niobate thin film. The design space of the SH0 mode ADLs at GHz is first theoretically investigated, showing that the large coupling and sufficient spectral clearance to adjacent modes collectively enable the broadband performance of SH0 delay lines.

High performance fully etched isotropic microring resonators in thin-film lithium niobate on insulator platform.

We present our design, fabrication, and experimental results for very high-performance isotropic microring resonators with small radii (∼ 30 µm) based on single-mode strip waveguides and transverse magnetic (TM) polarization in a fully etched lithium niobate (Z-cut) thin-film on insulator. The loss of the devices is predicted to be < 10 dB/cm, and is measured to be ∼ 7 dB/cm. The measured optical responses of microring resonators exhibit an extinction of ∼ 25 dB (close to critical coupling), a 3 dB optical bandwidth of 49 pm (∼ 6 GHz) for all-pass structures, an extinction of ∼ 10 dB for add-drop structures, and a free spectral range of ∼ 5.

Realization of alignment-tolerant grating couplers for z-cut thin-film lithium niobate.

We present the design, modeling, fabrication, and characterization of grating coupler devices for z-cut lithium niobate near 1550 nm. We first experimentally measure the sensitivity of the insertion loss of a conventional grating coupler to translational misalignment through a three-factor full factorial design of experiment. Next, we design grating couplers that are significantly less sensitive to misalignment.

Gigahertz Low-Loss and Wideband S0 Mode Lithium Niobate Acoustic Delay Lines.

We present the first group of gigahertz S0 mode low loss and wideband acoustic delay lines (ADLs). The ADLs use a single-phase unidirectional transducers (SPUDT) design to launch and propagate the S0 mode in an X-cut lithium niobate thin film with large electromechanical coupling and low damping. In this work, the theoretical performance bounds of S0 mode ADLs are first investigated, significantly surpassing those in state-of-the-art.

Feasibility of Intraocular Projection for Treatment of Intractable Corneal Opacity.

Despite many decades of research and development, corneal opacity remains a leading cause of reversible blindness worldwide. Corneal transplantation and keratoprosthesis can restore corneal clarity, but both have well-known limitations. High-resolution electronic microdisplays may offer an alternative to traditional methods of treating corneal disease using an intraocular implant to project imagery onto the retina, obviating the need for a clear cornea.

A Frequency Independent Framework for Synthesis of Programmable Non-reciprocal Networks.

Passive and linear nonreciprocal networks at microwave frequencies hold great promises in enabling new front-end architectures for wireless communication systems. Their non-reciprocity has been achieved by disrupting the time-reversal symmetry using various forms of biasing schemes, but only over a limited frequency range. Here we demonstrate a framework for synthesizing theoretically frequency-independent multi-port nonreciprocal networks.

Lithium Niobate Phononic Crystals for Tailoring Performance of RF Laterally Vibrating Devices.

This paper reports the first demonstration of phononic crystals (PnCs) in suspended lithium niobate thin films, which exhibit band gaps for tailoring the performance of laterally vibrating devices. Transmission and reflection properties of lithium niobate PnCs for both shear-horizontal (SH0) and length-extensional (S0) modes have been investigated and subsequently explored in two applications. In the first case, PnC-embedded delay lines were designed for filtering with stopbands, while in the second case, PnC-bounded resonators were implemented for spurious mode suppression.

Quantum dot emission modulation using piezoelectric photonic crystal MEMS resonators.

Quantum dots (QDs) integration into photonic devices requires varied approaches to control and modulate their emission. We demonstrate voltage-tunable PC structures with integrated QDs over suspended piezoelectric aluminum nitride thin film resonators that modulate PC enhancement at MHz frequencies. When the piezoelectric device is actuated at its resonant mechanical frequency, the extracted QD emission direction is likewise modulated via the optical resonant frequency of the PC.

Ultra-Small, High-Frequency, and Substrate-Immune Microtube Inductors Transformed from 2D to 3D.

Monolithic on-chip inductors are key passive devices in radio frequency integrated circuits (RFICs). Currently, 70-80% of the on-wafer area of most RFIC chips is occupied by the sprawling planar spiral inductors, and its operation frequency is limited to a few GHz. With continuous scaling of the transistor technology, miniaturization and high frequency operation of inductors have become the bottleneck to meet future demands of wireless communication systems.